Magnesium bodies

I really can't figure out why they would do this; if you're going to the trouble to use a metal frame, you really should attach the important parts (lens and sensor) to that frame; everything else can flap around freely but you do want the optics to be precisely located.

Actually, it's because engineering plastic really is perfectly sufficient and quite ideal for this purpose. The advantage of engineering plastic is that it's very rigid, and extremely moldable. The moldability is really quite key because it allows the engineers to create the exact, intricate shapes, struts, and details to the subframe that puts the material exactly where the stress points are. Plus, it's lightweight, and cost-effective. Also, keep in mind, this isn't just any old toy plastic. Plastic comes in a very broad range of compositions and characteristics, and there are a lot of ill-informed people who immediately think that "plastic" must mean cheap and poor quality. The reality is that, for the cost, weight, and rigidity, high carbon engineering plastic is the optimum material. To make the same kind of structure in metal, it would be
much
heavier and more costly, with little or no advantage. And the fact that there have literally been
millions of SLRs and DSLRs
that have been made with this plastic subframe structure is a testament to the fact that it really does work! It has definitely proven itself in the real world over the span of decades of camera manufacturing and millions of cameras.

A typical mirror box subframe structure made of high strength engineering plastic, onto which the lens mount, mirror mechanism, and sensor are attached:

In the structural diagram below, from dpreview's 500D review:

"...it's primarily made from three materials; a stainless steel chassis (blue in this diagram), the mirror box which is made of high-strength 'engineering plastic' (red in the diagram) and the body made of a special lightweight 'engineering plastic' which also provides some electromagnetic shielding. Construction is good (considering the budget price) with no creaks or rattles."

If you're putting the optical elements on plastic you might as well make the frame out of goat cheese.
--
Leonard Migliore

Believe it or not, the engineers that have designed these cameras might know a bit more about what it takes to make a structurally sound camera than you do. And clearly, after so many millions of cameras sold, it does appear that they are doing just fine without the input of armchair engineers on internet forums telling them that they are doing it all wrong. The fact that I can go out and buy an all-plastic Canon Rebel T3i, stick a heavy Canon L lens on it, and do a full shoot with it and get excellent, sharp results is a testament to the fact that today's cameras-- even the inexpensive plastic ones-- are quite well engineered.

While magnesium is touted for its stiffness, a downside of this stiffness is that magnesium body plates are unyielding and brittle, and therefore more prone to cracking if dropped. This is in contrast to polycarbonate plastic bodies, which can withstand impacts much better because plastic is much more resilient and dissipates shock much better. Here are just a few examples of cracked and damaged magnesium alloy camera bodies resulting from being dropped. As you can see, magnesium alloy isn't always what it's
cracked
up to be. (Sorry for the bad pun.)

If you're wondering how plastic would have fared in the same situations, here is a good example (below). This is a Canon 7D that has been dropped at the point where the back magnesium body plate and the bottom plastic body plate meet. As you can see, the plastic body plate survived but the magnesium body plate cracked and broke off. The impact force was severe enough to put a deep "compression wound" in the plastic. But the plastic still held up. Unfortunately, the same can not be said for the magnesium. Something tells me that the weather sealing on this 7D isn't going to be quite as good as it used to be!

It's for this reason that I would be much less worried about dropping my plastic Canon 60D than I would my magnesium Canon 40D. Plastic is just so much more resilient and can handle impact shock much better. That's why sports helmets are made of high tech plastics, not magnesium! The shock-dissipating properties of plastics are also probably better for the internal components of cameras too, just like a plastic helmet protects your sensitive brain tissue from impact shock.

If you've ever wondered just how much abuse today's modern plastic camera bodies can withstand, I suggest you watch this video where they put a plastic Nikon D90 and Canon 550D through a series of torture tests to demonstrate what these camera bodies can handle. This includes...

...pouring a full cup of hot tea on each camera...twice!

...tying them to the bottom of shoes and walking around with them:

...hammering nails with them:

...kicking a soccer ball at them while they are mounted on a tripod so they come crashing onto the concrete below:

...taking a blow torch to them:

...dropping a PC on them:

And after all this abuse, the cameras survived, and the testers take these cameras out for a photo shoot...on a rainy day, no less!

And keep in mind that these are cheaper, lower level bodies using a cheaper grade of plastic and lower level of build quality!

Whether YOU agree with it is moot, I still have and use 6- 35mm vintage cameras (4 diff. brands) and they are all in perfect working condition. Conversely I have a whole big box full of disabled and useless digital PLASTIC cameras that have 'bit the dust" and are only there for parts. History has borne out that the all metal mechanical cameras are vastly superior for longevity.

The reality is that today's plastic-bodied DSLRs will last just as long, if not longer, than your 35mm vintage cameras. First of all, today's DSLRs have far fewer moving parts. Secondly, they won't rust or corrode like metal cameras. The main thing that is going to render them unusable is the lack of battery power. But otherwise, they would just keep working until the shutter finally failed.

Just think of all those plastic bottles floating around in the ocean for years and years. A metal bottle would barely last a year or two in those conditions. Heck, just look at the condition of this Japanese ship that was swept out to sea during the Japan tsunami and was found drifting off the coast of Canada after a year at sea! That's what happens to metal over time.

You also have to consider that "metal mechanical cameras" get far, far less mileage (ie, number of shots) put on them than today's digital cameras. The cost of film and processing, combined with only being able to shoot 36 shots per roll, inevitably limited their use in a way that you just don't have with, for example, a DSLR. Typical film shooters using 35mm "metal mechanical cameras" might shoot a couple rolls per week (72 frames), whereas a DSLR shooter may shoot that many images per hour! These 35mm cameras are like lightly-driven cars compared to how many pictures people take these days with their digital cameras. Of course a camera and a car will seem to have greater longevity if they are barely driven!

I keep hearing about "build" quality of the new expensive cameras like Nikon, Canon, Sony.

Now I don't figure my camera is going to be run over by a car or truck so why add an expensive magnesium body to the build. New plastics are plenty strong for todays cameras.

What's more likely to happen is the camera will be dropped, the lens will be damaged or the more fragile insides will be damaged.

It seems better to add a thicker rubber coating to the camera to provide more protection than a stronger frame.

I dropped my Olympus E510 off my computer desk. It fell 2 feet onto a rug. No outside damage but the finder readouts and the flash stopped working. Now that wasn't even a hard fall.

Owen

Plastic may be adequate structurally, but it is an excellent insulator and really holds in the heat generated by the electronics and also solar gain on a sunny day. I prefer a magnesium body camera because of it's superior thermal qualities that dissipate heat much faster than plastic. A magnesium body camera remains noticeably cooler in my hand than a plastic body camera, and since I usually use a hand strap instead of a neck strap, my camera stays in my hand for long periods of time. I find a plastic body camera gets uncomfortably warm in a very short period of time. I think it is likely that a metal body also keeps the electronics cooler as well, for longer life and less heat generated sensor noise.
That's my two cents on the subject anyway.
--
"Pay no attention to that man behind the curtain! The Great Oz has spoken!"

I'm at photography for about 37 years and have owned tons of cameras. I think that this metal thing in expensive cameras is because people expect it. I've big cameras like 1SDsii and iii and 1Div. I wish they brought out lighter plastic versions with the same functions.
Metal dents if you drop it. Plastic doesn't.

I think that properly used, plastic is the superior material because of its ability to take a bang and because it's a helluva lot lighter.

Plastic may be adequate structurally, but it is an excellent insulator and really holds in the heat generated by the electronics and also solar gain on a sunny day. I prefer a magnesium body camera because of it's superior thermal qualities that dissipate heat much faster than plastic. A magnesium body camera remains noticeably cooler in my hand than a plastic body camera, and since I usually use a hand strap instead of a neck strap, my camera stays in my hand for long periods of time. I find a plastic body camera gets uncomfortably warm in a very short period of time. I think it is likely that a metal body also keeps the electronics cooler as well, for longer life and less heat generated sensor noise.
That's my two cents on the subject anyway.

I don't find that to be true at all. I shoot weddings and events all day with a 40D (magnesium), 5D (magnesium), and 60D (plastic), and I find no difference in the temperature of any of these cameras. In no way does my plastic-bodied 60D get "uncomfortably warm in a very short period of time", nor does it get that way in a very long period of time. Nor have I ever seen it reported that any of the other millions of plastic DSLR bodies being used out in the wild (popular cameras like the Canon Rebel T3i's, Nikon D5100's, etc.) get "uncomfortably warm". And plastic-bodied DSLRs are by far the most widely sold cameras out there!

Even with extensive video shooting on my Canon 60D, the camera does not get any warmer than my 5D or 40D that don't shoot video! One would expect that if there were any situation where you could generate a significant and noticeable difference in camera temperature, it would be with video shooting...especially with a plastic body that is supposedly retaining all the heat generated by video shooting. But that simply isn't the case.

You also have to remember that most magnesium bodies have a core of high strength engineering plastic. It might be metal on the outside, but it's plastic on the inside.

Plastic is subject to material failure through temperature and normal fatigue of plastic materials. I have a fairly large box of computer 'parts" from a half dozen digital cameras made since 1999. All of them failed due to the plastic GEARS shedding their teeth and no repair parts are abailable. Plastics DO deteriorate over time, all of the plastic apparatus I have including chairs, kitchen appliances, automobile parts fail rather rapidly in the tropics either from temperature or humidity change but in fact plastic fails. Metal parts do not fail in the same time period, I have several old cameras dating back to my 1932 Kodak Recomar and none of them have failed.

You "spends yer money and you takes yer chances", my money goes with the metal bodies. That isn't to say that many of the so-called metal bodies are merely metal "shells" over plastic guts such as all of the Canon mid class "D" series until the 7D, the light boxes and basic chassis are all plastic. The 1D series by contrast are ALL metal, you get what you pay for.--

' You don't have to have the best of everything to get the best out of what you do have'.

All of them failed due to the plastic GEARS shedding their teeth and no repair parts are abailable.

LOL, what kind of DSLRs are you using that have "gears" that are shredding their teeth! Last time I checked, DSLRs had no such gears inside them!

You also have to understand that there is an extremely broad range of plastics. For example, some of the touchest storage boxes you can buy are Pelican cases, whcih are made of plastic. These plastic Pelican cases are virtually indestructible, can handle a huge range of temperatures without failing or fatiguing, and are tough enough to stand up to military use:

In all probability I was using Pelican cases before you were even born but they do not comprise the internal parts of digital cameras. I did not say DSLR gears but I states "digital camera" focusing gears, so if they fail the rest of the plastic parts are suject to failure on DSLR's. Learn to read please.
--

' You don't have to have the best of everything to get the best out of what you do have'.

You are referring to Canon primarily and they were guilty of using a plastic chassis with magnesium shells. Which is akin to putting "whipped cream on a horse biscuit".. My Nikon D200, D2x are ALL magnesium as is the case in some of the newer Canon mid class cameras, the 1D series have always been total mag bodies and there is a ton of difference between the two series other than just the shells. The shutters, sensors (according to Canon) and the general construction is akin to comparing a Yugo to a Mercedes.

The basic reason magnesium is used in Pro Level cameras is basic, it's is simply a better material if used in rough and adverse conditions. I packed a Speed Graphic for 8 years in the Navy and military cameras had to survive many endurance tests before they were adopted for military use. I never saw a PLASTIC FANTASTIC all the time I was in the service.....HMMMM, I wonder why?
--

' You don't have to have the best of everything to get the best out of what you do have'.

I keep hearing about "build" quality of the new expensive cameras like Nikon, Canon, Sony.

Now I don't figure my camera is going to be run over by a car or truck so why add an expensive magnesium body to the build. New plastics are plenty strong for todays cameras.

Right plastics should be the future here. Plastics will also flex some helping to slow down impact providing less of a shock to a fallen camera. Just like airbags slow people down.

I dropped my Olympus E510 off my computer desk. It fell 2 feet onto a rug. No outside damage but the finder readouts and the flash stopped working. Now that wasn't even a hard fall.

That is sad. I had my Canon 5D get pulled out of my hand from about 3 feet and fell down onto asphalt (I actually stepped on the strap). A couple of scrapes but absolutely no operation of the camera was affected and that was 2 or more years ago.

You are referring to Canon primarily and they were guilty of using a plastic chassis with magnesium shells.

I hate to break it to you, but this is a Nikon body:

The basic reason magnesium is used in Pro Level cameras is basic, it's is simply a better material if used in rough and adverse conditions. I packed a Speed Graphic for 8 years in the Navy and military cameras had to survive many endurance tests before they were adopted for military use. I never saw a PLASTIC FANTASTIC all the time I was in the service.....HMMMM, I wonder why?

You wonder why? Probably because you were enlisted during World War II, before the age of modern plastics? LOL.

What you fail to realize is that many of the latest, modern assault rifles make heavy use of plastics. Why? Because they don't corrode, have greater temperature stability, are lighter, absorb shock/vibration better, etc.

Consider that the latest generation of high tech military assault rifles are being made of plastics! Yes, plastics are being applied to the latest military assault rifles because they provide for a strong, durable, resilient weapon that is also lighter. The following are all military assault rifles that have plastic body frames. And no, I do not mean "plastic over metal subframe". I mean a true plastic body frame. The gun barrel and springs and small mechanicals inside the body frames are still metal, but the structural body frames are plastic. These are the next generation of weapons that the soldiers of tomorrow will be carrying. Lighter, with less metal and more plastics.

Here's the Israeli Tavor 21 (bottom) alongside the HK SL8-4 (top), both of which have plastic bodies. These are the latest generation of military assault rifles. And, as I mentioned, these are not "plastic over a metal subframe". Their body frames are actually injection-molded plastic.

Here are other plastic-bodied military assault rifles:

And yes, even good old Smith and Wesson recently introduced an updated, all-plastic (except for the barrel) version of their venerable AR-15 (you might know it better by the US Military's designation: the M-16) that is said to be every bit as good as the standard model, but a lot lighter! This plastic version is called the M&P 15-22.

And it even won Smith and Wesson the 2010 Rifle of the Year Award from the shooting industry.

Oh, and I should add that to the best of my knowledge I know of no assault rifles with magnesium alloy frames or bodies. I know some air guns and paintball guns use some magnesium components, but by and large you rarely see magnesium used in real weaponry. And obviously, nowhere to the same degree that plastics are being used! Gee, I wonder why? (It's because magnesium is brittle and prone to cracking.)

It's funny that plastics are good enough for the latest military assault rifles, but your average weekend warrior photographer thinks it's not good enough for a DSLR! And conversely, you hardly see magnesium used at all in military weaponry, and certainly not to the extent of having an assault rifle body frame made from magnesium, and yet some photographers think it's a miracle metal! Maybe weapons designers and testers and military weapons experts know something that the average magnesium-adoring photographer doesn't know? I'd be surprised if weapons designers hadn't considered all potential materials, including all types of magnesium alloys and plastics. I'm sure these weapons designers tried out the same magnesium-molding processes that camera manufacturers use to make their magnesium cameras, testing out magnesium-framed weapons just like they did with plastic, and maybe they found out that magnesium
just wasn't all that it was cracked up to be?
And somehow these different weapons manufacturers all started using plastics for their body frames? Not magnesium? Hmmm.

Hopefully, this will get people to re-think their false notion that plastic is such an inferior material and magnesium is such a superior material. If plastics are good enough for hotshoe flashes, lenses, and today's toughest military forces, I'm pretty sure it should be good enough for a DSLR body.

Plastic is subject to material failure through temperature and normal fatigue of plastic materials. I have a fairly large box of computer 'parts" from a half dozen digital cameras made since 1999. All of them failed due to the plastic GEARS shedding their teeth and no repair parts are abailable.

Plastic gears in digital camera? You must be talking about motorized zoom lenses which are not in digital SLRs. So it's a non-issue for the OP's issue since he has a dSLR.

Plastics DO deteriorate over time, all of the plastic apparatus I have including chairs, kitchen appliances, automobile parts fail rather rapidly in the tropics either from temperature or humidity change but in fact plastic fails.

In those same humid conditions being outside, metal rusts when plastic won't.

You are referring to Canon primarily and they were guilty of using a plastic chassis with magnesium shells. Which is akin to putting "whipped cream on a horse biscuit".. My Nikon D200, D2x are ALL magnesium as is the case in some of the newer Canon mid class cameras

Just how many digital SLRs have you heard of that fell apart because they were not 100% metal shells? I certainly haven't heard of any.

Hand held devices should be designed with the latest materials, not materials from WW II. If I'm going to carry an SLR in my hand or around my shoulder for house, I want it to be as light as possible and still durable. Heavy cameras cause health problems.

In all probability I was using Pelican cases before you were even born but they do not comprise the internal parts of digital cameras. I did not say DSLR gears but I states "digital camera" focusing gears, so if they fail the rest of the plastic parts are suject to failure on DSLR's. Learn to read please.

Sorry to break it to you, but you continue to be woefully uninformed. The same glass-reinforced plastics used in many Pelican cases are the same or very similar types of plastics used inside digital cameras:

As for your "focusing gears" non-sense, the types of plastics used in an inexpensive consumer pocket digicam are not necessarily the same plastics used in a DSLR. You continue to ignorantly assume that all plastics are the same. That simply is not true.

There is a huge and broad range of plastics, and the fact that there are literally
millions
of plastic DSLR cameras, in addition to magnesium DSLR cameras with plastic sub-frames, that have been sold and put into use over the last decade is a testament to the fact that plastics definitely are up to the task.

And just because you have a bunch of "digital cameras" with broken "focusing gears" doesn't mean that this relates to DSLR cameras because A) we're probably talking about completely different types of plastics, B) there really aren't many moving parts inside a DSLR anyways, and C) parts inside a DSLR are made of different materials, based on the requirements of that particular part; sometimes the component may be metal, sometimes it may be plastic, but suffice it to say that the engineers have chosen the optimum material for the task to be performed inside a DSLR.

You can't compare the plastic in your lawn chair to high-tech plastics as used for camera bodies. You also can't compare across applications -- like gears vs. bodies vs. lenses. Gears should be made of steel. These need to be hard enough to not to wear down. Springs should be steel too. There are lens parts that need to be super-stiff in compact form factors. There, you do want super-rigid materials. There's a difference between hardness, fatigue life, stiffness, etc. You have different constraints for different engineering applications.

For the camera body, I'm inclined to agree that plastic is the right material for the job for most applications.